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99 cooling fan issue

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spidyrmen

New member
I have a 99 grand prix that has 106,000 miles on it. My car overheats at idle because the cooling fans don't turn on. One however does come on whaen the a/c is turned on. Also when I unplug the plug from the sensor both fans come on but the temp guage goes out. When i plug the sensor back in the temp guage starts to work and both fans stay on until I turn the car off and restart it. The fans do not turn back on. I have replaced the sensor and have checked both relays and they are fine. The man at autozone told me that there was another sensor to control the fans but i can't find it and my haynes manual doesn't show it. thank you very much i would appreciate the help
 


its a 3 wire sensor, he is full of ****. When mine went out, the scan gauge read -38 degrees on the coolant temp, dash cluster coolant temp was reading fine, and fans came on with a/c, just not when it would heat up. It was the coolant temp sensor bad. It has one signal that goes to the dash and one signal that goes to the computer. If it goes bad on one end, it will read fine on the dash but will never signal computer to kick on the fans. However, in your case, idk. Maybe another relay that just the computer uses?

Logan
 
@spidyrmen: I'm pretty sure that there are three relays for the fans and at least one fuse. Did you check everything?

@minichopper: What engine do you have?
 


hey names matt im new here and i also have the same problem with my 99 gtp but my fans do not come on at all . when i got the car a few days ago the pre owner had wired the fans to a toggle under the hood .I removed all the crap he put in and re wired the fans back to the factory plug changed the 3 relays under the hood and the 40amp fuse as well also the coolant temp sens ...... im at a loss here can anybody help thanks for youre time
 
I had this problem on another GP.... I just hardwired my fans to a switch inside the car (with the slice joint things, I didn't cut the wires). Problem solved. Wire, fuse, switches are cheaper then trying to troubleshoot... If they worked the worked, if they didn't and I saw my temp starting to rise through town with many stops I just flipped the switch... LOL just my $.02
 


I Haven't checked schematics on you particular car, but the fan is controlled by the computer, if you unplug the temp sensor the computer commands both fans on knowing their is a potential problem in which it cannot track engine temps. When you say they don't come on, how high is the temp gauge getting up to? Many times sitting at idle with your hood open, it is tough to get the engine hot enough to turn the secondary fan on period. These engines cool Pretty efficiently. The fans kick on with the a/c on, right?

chris
 
i've got a 95 gtp and have this problem... its weird, when i turn my ac on the fans would click on, but eventually my ac went out, fans didnt work, ran out of coolant uenxpectedly and blew a head gasket... now im back up and running, both fans work but my temp gauge doesnt work... i think that must be the empty sensor spot we cant find to plug in
 
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